Prince William and 20 close pals celebrated the prince's final few weeks of singledom at a country estate in Norfolk, England.
The secret bachelor party took place just two hours outside London.
"We believe that William had a house party effectively within the grounds of a big stately home owned by friend Ed Van Cutsen, he's one of the ushers at the wedding," said ABC News contributor Duncan Larcombe.
The all-boys-bash was planned by Guy Pelly and William's younger brother Prince Harry.
Harry had originally planned a water-themed celebration with speed boats and water skiing, but these plans were dropped after details leaked to the press.
"He did everything he could to stay out of the public eye," said Larcombe. "The shy prince does it again, no one got near him."
That shy one would be Will of course, not Harry.
As for Harry, seeing out his brother's days of bachelorhood came just a few days before he is due in the North Pole where he will take part in a four-week, 200-mile journey for charity.
"This was a logical weekend for them -- Williams just got back from Australia, there weren't that many dates left," Larcombe told ABC News.
So what about Kate's bachelorette party?
"Well, we know that's coming," said royal author Katie Nicholl. "I'm hearing possibly next weekend."
"It's probably going to be at the Middleton family home," continued Nicholl. "Although they have hired out four venues in London in case they want to hit the capital."
So, it seems secrecy is again the name of the game.